As an alternative or add-on to satellite-based positioning systems, positioning systems in which a present position of a terminal is estimated based on a list of Coverage-Providing Entities (CPEs) (such as for instance base stations of a cellular Communication System (CS), or Wireless Local Area Network (WLAN) Access Points (APs)) that can presently be “heard” by the terminal and a database that contains identifiers and positions of the CPEs and/or models for their coverage areas (e.g. elliptical models) have gained recent interest. Therein, a terminal may for instance be considered to “hear” a CPE if it is able to receive one or more signals (e.g. a broadcast channel), which are sent by the CPE, with a pre-defined minimum quality (for instance defined in terms of a signal-to-noise ratio or a signal-to-noise and interference ratio), or if the terminal is capable of at least partially receiving and correctly decoding one or more signals sent by the CPE (e.g. a broadcast channel), or if the terminal is able to receive and correctly decode a CPE identifier (for instance a Medium Access Control (MAC) address or another identifier). The information which communication nodes a terminal can hear may for instance result from a scanning/sniffing operation performed by the terminal.
For instance, given that the positions of the heard CPEs are known and distances from the terminal to the heard CPEs can be estimated, the terminal's position can be estimated through triangulation. The distance between a terminal and the heard CPEs can for instance be estimated based on the path loss using a channel model (i.e. how much the signal attenuates between the terminal and the CPE) or based on timing (or round-trip timing) measurements (i.e. information expressing how long signals propagate between terminal and CPE).
Alternatively, if coverage area models of CPEs are known, a terminal may pick the coverage area models for the heard CPEs and find the intersection of these coverage area models. The terminal can then be assigned a position that is, for instance, the center-of-mass of the intersection area. Similarly an error estimate for the position estimate can be given, for example, based on the size of the intersection.